Advanced metal alloys with high strength and high fracture toughness are used in an increasing number of applications. However, the use of some metal alloys, including Al—Cu alloys, as critical structural components has been limited due to their poor weldability. The weldability of alloys depends upon their chemical composition and is generally defined qualitatively by investigating final weld quality. The extent of hot cracking defects in a weld is one measure of a material's weldability. Hot cracking is caused by solidification shrinkage and thermal contraction during weld cooling. Conventional approaches to reducing the hot cracking susceptibility of a weld have included changing the welding processing parameters (e.g., pre-heating, welding speed, etc.) or modifying the filler metal of the welding material. Unfortunately, these methods have met with limited success.